Conference Paper

Robust and Sustainable Schedulability Analysis of Embedded Software

DOI: 10.1145/1379023.1375666 Conference: Proceedings of the 2008 ACM SIGPLAN/SIGBED Conference on Languages, Compilers, and Tools for Embedded Systems (LCTES'08), Tucson, AZ, USA, June 12-13, 2008
Source: DBLP

ABSTRACT For real-time systems, most of the analysis involves efficient or exact schedulability checking. While this is important, analysis is often based on the assumption that the task parameters such as execution requirements and inter-arrival times between jobs are known exactly. In most cases, however, only a worst-case estimate of these quantities is available at the time of analysis. It is therefore imperative that schedulability analysis hold for better parameter values (Sustainable Analysis). On the other hand, if the task or system parameters turn out to be worse off, then the analysis should tolerate some deterioration (Robust Analysis). Robust analysis is especially important, because the implication of task schedulability is often weakened in the presence of optimizations that are performed on its code, or dynamic system parameters. In this work, we define and address sustainability and robustness questions for analysis of embedded real-time software that is modeled by conditional real-time tasks. Specifically, we show that, while the analysis is sustainable for changes in the task such as lower job execution times and increased relative deadlines, it is not the case for code changes such as job splitting and reordering. We discuss the impact of these results in the context of common compiler optimizations, and then develop robust schedulability techniques for operations where the original analysis is not sustainable.

Download full-text

Full-text

Available from: Insup Lee, Aug 25, 2015
0 Followers
 · 
81 Views
  • Source
    • "In such a case, any schedule for the top-level tasks is robust and sustainable (in the sense of e.g. [14], [15]) to a replacement of an abstract task by any of its refinements. For schedulability at the top level, standard periodic-task scheduling techniques can be used (c.f. "
    [Show abstract] [Hide abstract]
    ABSTRACT: The Hierarchical Timing Language (HTL) is a real-time coordination language for distributed control systems. HTL programs must be checked for well-formedness, race freedom, transmission safety (schedulability of inter-host communication), and time safety (schedulability of host computation). We present a modular abstract syntax and semantics for HTL, modular checks of well-formedness, race freedom, and transmission safety, and modular code distribution. Our contributions here complement previous results on HTL time safety and modular code generation. Modularity in HTL can be utilized in easy program composition as well as fast program analysis and code generation, but also in so-called runtime patching, where program components may be modified at runtime.
    01/2009; DOI:10.1109/RTSS.2009.9
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: With an increasing number of applications, real-time embedded systems are gaining in size and complexity. Many of these systems are complex as a whole, but consist of smaller modules interacting with each other. This structure makes them amenable to compositional design. For real-time systems, compositional design is done using models consisting of components arranged in a scheduling hierarchy. Analysis of such systems depends on the choice of the task model and the interfaces used to abstract component timing requirements. Real-time applications have been traditionally modeled either as periodic and sporadic tasks which are easy to analyze but simplistic, or as task graphs and automata models that are very expressive, but complex to analyze, especially with respect to compositional analysis. We develop conditional task models with a view to claim the middle ground. We show that these models, while being expressive enough to capture conditional release of jobs, or dependencies between tasks, also allow for efficient analysis. We establish results for checking schedulability of task sets comprising of conditional tasks, and techniques to compositionally analyze a hierarchical resource sharing system where each component comprises of conditional tasks. Schedulability analysis of tasks is based on the assumption that the task parameters such as execution requirements and inter-arrival times between jobs are known exactly. In most cases however, only an estimate of these quantities is available at the time of analysis. If the task parameters turn out to be better than those considered, then the analysis should be sustainable with the new parameter values. If the task parameters turn out to be worse off, then the analysis should be robust enough to tolerate some deterioration. With this view, we introduce and address sustainability and robustness questions for analysis with conditional tasks. Finally, the introduced models and compositional analysis techniques are illustrated with an automotive case study. The study clearly demonstrates the utility of introduced techniques over previous approaches for compositional analysis.
  • [Show abstract] [Hide abstract]
    ABSTRACT: To examine the role of sex and marital status in the distribution and consequences of cardiovascular risk factors for stroke. Longitudinal cohort. U.S. national sample, community based. U.S. adults aged 50 and older and their spouses. Health and Retirement Study (HRS) participants born between 1900 and 1947 (N=22,818), aged 50 and older, and stroke-free at baseline were followed an average of 9.4 years for self- or proxy-reported stroke (2,372 events). Financial resources, behavioral risk factors, and cardiovascular conditions were used to predict incident stroke in Cox proportional hazard models stratified according to sex and marital status (married, widowed, divorced or separated, or never married). Women were less likely to be married than men. The distribution of risk factors differed according to sex and marital status. Men had higher incident stroke rates than women, even after full risk factor adjustment (hazard ratio (HR)=1.22, 95% confidence interval (CI)=1.11-1.34). For both sexes, being never married or widowed predicted greater risk, associations that were attenuated after adjustment for financial resources. Widowed men had the highest risk (HR=1.40, 95% CI=1.12-1.74 vs married women). Lower income and wealth were associated with similarly high risk across subgroups, although this risk factor especially affected unmarried women, with this group reporting the lowest income and wealth levels. Most other risk factors had similar HRs across subgroups, although moderate alcohol use did not predict lower stroke risk in unmarried women. Stroke incidence and risk factors vary substantially according to sex and marital status. It is likely that gendered social experiences, such as marriage and socioeconomic disadvantage, mediate pathways linking sex and stroke.
    Journal of the American Geriatrics Society 10/2009; 57(12):2293-9. DOI:10.1111/j.1532-5415.2009.02555.x · 4.22 Impact Factor
Show more